Preparation And Performance Of Thermo-Sensitive Pyraclostrobin Microcapsules

Pyraclostrobin is a new active substance with fungicidal properties that belongs to a group of synthetic fungicides called strobilurins which behave similarly to the natural strobiurin-A.It demonstrated that pyraclostrobin showed high efficiency on controlling of rice blast,and pyraclostrobin was highly toxic to aquatic organisms.It is of great significance to achieve safety of pyraclostrobin applied on rice by constructing pyraclostrobin microcapsules based on temperature-responsive and reducing the risk of pyraclostrobin on aquatic organisms.Thermo-sensitivepyraclostrobinmicrocapsuleswereobtainedviaemulsion polymerization and solvent evaporation method with P?NIPAM-co-BA?andP??-CD-co-PBS-co-NIPAM?as wall material.In this paper,relevant study on properties characterization and safety evaluation of microcapsuleswere conducted.The main researches were as follows:Thermo-sensitivepyraclostrobinmicrocapsuleswereobtainedviaemulsion polymerization successfully in this paper.The morphology,average diameter,the drug loading and encapsulation efficiency of microcapsules were characterized by scanning electron microscope,optical microscope,automatic laser granularity analyzer,ultraviolet spectrophotometer.Its controlled-release performance and release kinetics was studied by dialysis bag method.The results showed that the obtained microcapsules had a smooth and spherical surface,and average diameter of thermo-sensitive pyraclostrobin microcapsule was1.04?m.The drug loading and encapsulation efficiency of thermo-sensitive pyraclostrobin microcapsules were respectively 15.66%and 78.30%.The results also showed that pyraclostrobin microcapsules had representative temperature-sensitive,and the responsive temperature of microcapsule was about 28.2?.It could release the active ingredient of controlled-release in accordance with the environment temperature difference.When the environment temperature was higher than 28.2?,the microcapsule could release the active ingredient rapidly,and the environment temperature was lower than 28.2?,its release behavior was restrained.The release of microcapsule at 20?was fitted with zero order release-kinetic equation.The release of microcapsule at 35?was fitted with the first order release-kinetic equation.Thermo-sensitive pyraclostrobin microcapsules were obtained via solvent evaporation method successfully in this paper.The microcapsules were charactered by scanning electron microscope,optical microscope,automatic laser granularity analyzer,X-ray diffractomer,high performance liquid chromatography.Its controlled-release performance and release kinetics was studied by dialysis bag method.The results showed that the obtained microcapsules had a smooth and spherical surface,and average diameter of thermo-sensitive pyraclostrobin microcapsule was 7.08?m.The drug loading and encapsulation efficiency of thermo-sensitive pyraclostrobin microcapsules were respectively 14.99%and 52.91%.The XRD results suggested that pyraclostrobin was loaded in microcapsules.The results also showedthatthermo-sensitivepyraclostrobinmicrocapsuleshadrepresentative temperature-sensitive characters,and the responsive temperature of microcapsule was about25.0?.It could release the active ingredient of controlled-release in accordance with the environment temperature difference.Microcapsules would exhibit a faster release rate of pyraclostrobin in 35?,while microcapsules would be inhibited the release of pyraclostrobin in 20?.The release of microcapsule at 20?and 35?was fitted with the first order release-kinetic equation.The acute toxicity of zebrafish was determined by semi static method,the results showed that:The LC₅₀?96 h?value of thermo-sensitive pyraclostrobin microcapsules with P?NIPAM-co-BA?as wall material was 4.48 mg a.i./L,it raised more than 90 times than LC₅₀?96 h?value of pyraclostrobin technical.The LC₅₀?96 h?value of thermo-sensitive pyraclostrobin microcapsuleswith P??-CD-co-PBS-co-NIPAM?as wall material was 7.71 mg a.i./L.it raised more than 150 times than LC50?96 h?value of pyraclostrobin technical.